I'm honestly amazed by people being surprised that he could take the items with him. The fact that he had taken on this form, separated from his body, to search for the grass in the first place, would seem to indicate that he would be able to take the grass with him back to his actual body, because otherwise it wouldn't make much sense for him to be searching in this manner (which has an additional danger of possibly turning himself into an undead). Since he appears to be using magic to search in this manner, it also makes sense to answer the question of "how can he take the physical grass with him" being the use of magic, as well.